You have sucessfully inserted a video from Website in
PowerPoint 2010 but suddenly the video doesn't play.

If you try to preview it (RIGHT click in edit mode >
Preview) you get a message to install a
later version of Flash Player. Problem is you already have the latest
version!

Good News - It might be
possible to fix this

You Tube have moved the goalposts at least twice since the
original fix we posted. This fix seems to work in 2010 Office at the moment
and in some versions of 2013. We have no idea when the goalposts will move
again though. THEY HAVE SEE BELOW

Typical Insert

Lets look at some typical insert code, yours may be
different. Note how the version appears twice.

Notice that version=3 appears twice and the URL starts with
//www.youtube.com (TWICE).

Change version=3 to version=2 in both places and add http: before the URL as
below.

Hopefully it will now play!

We now have both a FREE AddIn that
(at the moment!) can deduce the correct embed code from the URL of the You
Tube AND automate the old 2007 insert Shockwave method which will usually
work in 2010 / 2013

UPDATE #42

Looks like Microsoft have removed the embed code
feature in 2013 altogether. presumeably while they work on a fix. The OLD
INSERT still seems to work with the free addin and if you have access to
2010 inserting (using the code generator in the addin) seems to work and the
saved file plays for us in 2013. But see below!

Update 42 and a bit

Just when you thought they couldn't make it worse .. an
update on Sept 12th killed the menu for Insert from web in 2010 as well.

The update is KB 2553145. At your own risk uninstall,
set updates to "Download and let me decide to install". When it reappears
right click and set to hidden. Hopefully the menu is back! If you do not
know how to do this we have deliberately not given instructions! We suggest
you find someone who knows how!

And a bit more:

15th September we got a stack more updates and the menu
has gone again! Uninstalling KB 2553145 didn't seem always to work this time. We did a system
restore to the day before and switched
updates to manual. Installed everything EXCEPT KB2553145 and it worked. Set
KB2553145 back to hidden again! This is probably because we had already un
installed the previous update. Uninstall may work for you.

We Have a New Version of Our Completely FREE AddIn

It can calculate the correct code (if you still have the
"Insert From Web" menu), provides an alternative way to insert You Tube
videos if the menu has gone and in some cases can fix existing faulty
inserts. No guarantee or support but FREE!

Note: If you haven't got the option to use embed code then obviously this
section is of little use to you. BUT .... You should find Option 2 "Old
Style Insert" still works and at least gives you the ability to use You Tube
video. The Fix button may fix old inserts.